Examples of methods of forming a stator winding of the rotary electric machine include a method using a concentric wound coil and a method using a lap wound coil. The concentric wound coil is configured by combining plural concentric coils having different diameters which are arranged concentrically so that the diameters of the coils become gradually greater. The perimeters of the coils used in the concentric wound coil become greater toward the radially outward side of the concentric wound coil. The portions of the stator winding located outside the slots do not contribute to the performance of the stator winding. Thus, in a stator winding employing a concentrically wound coil, greater amount of wasteful portions exist in the radially outward side of the coil.
The lap wound coil, on the other hand, is configured by disposing plural coils having the same diameter one over the other in the radial direction of the stator while shifting the slots in which the coils are inserted. The amount of portions of stator windings located outside the slots are less in a lap wound coil compared to a concentric wound coil and thus, there is less waste in the windings in a lap wound coil. However, arrangement of the lap wound coil is much more complicated compared to the concentric wound coil. Because the lap wound coil requires large number of windings with poor arrangement flexibility, it is difficult to insert the windings into the slots of the stator core. It has thus, been difficult to mechanize the task of inserting coils in a configuration employing a lap wound coil.